Hyundai Repair: 2006 Sonata Rear Window Defroster, diagnostic time, tint shop

Question
Recently I needed to use my rear defroster and noticed it was not working.  Nine months ago I tinted my windows so I took the car back to them to see if they may have disconnected something.  The window tint shop said they cut the tint to the size of the window and do not go under any molding in the rear window.  The cut of the tint does not extend beyond the exposed window.  They even performed a minor electrical test showing there is 12 volts at the window where the clips are but they say the clip (on the drivers side) may have become separated saying they have seen it before on Hyundai.  Specifically when the window is installed sometimes it cracks snapping the clip.

I took it to the dealer and when I told them about the tinting they said the warranty would not apply if the window needed replacement.  They will perform a diagnostics on the electrical problem in a couple of weeks.  The dealer (sales persons) suggested and recommended window tinting and told me where to go to get it done.  Do I have recourse, if they claim the warranty is voided due to the tinting?  The sales persons did suggest and recommend tinting.  

What is your experience working with Hyundai direct where there is a difference of opinions?  Do they work with the customer?

Answer
The only reason this repair should not be covered under your warranty is if the failure is due to the tinting or its installation.  If the dealer claims the issue is due to the tinting, they should be able to show you why that is the case.  Keep in mind that if the problem is indeed due to the tint, that you should expect to pay the dealer for their diagnostic time.  Hyundai won't reimburse them for their time if it's not a warrantable issue.

If you feel when you return to the dealer that they're not being fair with you, you should speak with the service manager or director there.  Calmly explain to the service manager/director why you think they're not being fair with you.  If you still think the dealer is being unfair, contact Hyundai customer assistance (1-800-633-5151).  I've found Hyundai to  never be less than fair with customers.  Considering you're a recent new vehicle purchaser, the factory representative will be especially receptive to things that will keep you happy.  The company would like you to purchase another vehicle from them.